Aircraft environmental control system

ABSTRACT

A compressing device for use in an environmental control system includes at least one turbine configured to provide energy by expanding one or more mediums. The one or more mediums provided at an outlet of the at least one turbine form a heat sink within the environmental control system. A compressor is configured to receive energy from the one or more mediums expanded across the at least one turbine. During a first mode of the compressing device, energy derived from a first medium and a second medium of the one or more mediums is used to compress a second medium at the compressor. During a second mode of the compressing device, energy derived from the first medium, the second medium, and a third medium of the one or more mediums is used to compress the second medium at the compressor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/058,834 filed Jul. 30, 2021, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND

Embodiments of the disclosure relate to environmental control systems,and more specifically to an environmental control system of an aircraft.

Aircraft need to have their internal environment controlled. In general,contemporary air conditioning systems are supplied a pressure at cruisethat is approximately 30 psig to 35 psig. The trend in the aerospaceindustry today is towards systems with higher efficiency. One approachto improve efficiency of an aircraft environmental control system is toeliminate the bleed air entirely and use electrical power to compressoutside air. A second approach is to use lower engine pressure. Thethird approach is to use the energy in the cabin outflow air to compressoutside air and bring it into the cabin. Each of these approachesprovides a reduction in airplane fuel burn.

BRIEF DESCRIPTION

According to an embodiment, an environmental control system of anaircraft includes a ram air circuit including a ram air shell having atleast one heat exchanger positioned therein and a divider arrangedwithin the ram air shell to separate the ram air shell into a firstregion and a second region. The at least one heat exchanger is arrangedwithin both the first region and the second region. A first medium isconfigured to flow through the first region and a second, distinctmedium is configured to flow through the second region. Theenvironmental control system additionally includes a dehumidificationsystem arranged in fluid communication with the ram air circuit and acompression device arranged in fluid communication with the ram aircircuit and the dehumidification system.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one heat exchangerincludes a first portion arranged within the first region and a secondportion arranged within the second region, the second portion of the atleast one heat exchanger is integrally formed with the first portion.

In addition to one or more of the features described above, or as analternative, in further embodiments the second portion of the heatexchanger is a condenser of the dehumidification system.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one heat exchangerincludes a first heat exchanger arranged within the first region and asecond heat exchanger arranged within the second region, the second heatexchanger being separate from and arranged in fluid communication withan outlet of the first heat exchanger.

In addition to one or more of the features described above, or as analternative, in further embodiments the first medium is ram air.

In addition to one or more of the features described above, or as analternative, in further embodiments the medium configured to flowthrough the second region is exhausted from the turbine of thecompression device.

In addition to one or more of the features described above, or as analternative, in further embodiments the medium configured to flowthrough the second region is bleed air.

In addition to one or more of the features described above, or as analternative, in further embodiments the medium configured to flowthrough the second region is a mixture of bleed air and cabin dischargeair.

In addition to one or more of the features described above, or as analternative, in further embodiments comprising a fan arranged within theram air shell to move the first medium across the at least one heatexchanger within the first region.

In addition to one or more of the features described above, or as analternative, in further embodiments the fan is separate from thecompression device.

In addition to one or more of the features described above, or as analternative, in further embodiments the fan is electrically powered.

In addition to one or more of the features described above, or as analternative, in further embodiments the fan is driven by a flow ofmedium provided thereto.

According to an embodiment, an environmental control system of anaircraft includes a plurality of inlets for receiving a plurality ofmediums including a first medium and a second medium and an outlet fordelivering a conditioned form of the second medium to at least one loadof the aircraft. A ram air circuit includes a ram air shell having atleast one heat exchanger positioned therein and a dehumidificationsystem is arranged in fluid communication with the ram air circuit. Acompression device is arranged in fluid communication with the ram aircircuit and the dehumidification system. The compression device includesa compressor and a plurality of turbines including a first turbine and asecond turbine operably coupled by a shaft. An outlet of the firstturbine is directly coupled to an inlet of the second turbine, such thatthe first medium is provided to the first turbine and the second turbinein series.

In addition to one or more of the features described above, or as analternative, in further embodiments the compressor is operable toreceive a second medium, and the compressor is driven by work extractedfrom the first medium within the first turbine and the second turbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the first medium is bleed air andthe second medium is fresh air.

In addition to one or more of the features described above, or as analternative, in further embodiments plurality of turbines furthercomprises a third turbine, wherein an inlet of the third turbine isarranged in fluid communication with an outlet of the compressor.

In addition to one or more of the features described above, or as analternative, in further embodiments the plurality of mediums includes athird medium and a flow of the third medium is arranged in fluidcommunication with the inlet of the second turbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the second medium and the thirdmedium are mixed at a mixing point located upstream from the secondturbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the second medium and the thirdmedium are mixed at a mixing point located at an outlet of the secondturbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the second turbine is a dual entryturbine having a first nozzle and a second nozzle, the outlet of thefirst turbine being directly coupled to the first nozzle, and the flowof third medium being connected to the second nozzle.

In addition to one or more of the features described above, or as analternative, in further embodiments a flow output from the secondturbine is used to cool a flow within the dehumidification system.

In addition to one or more of the features described above, or as analternative, in further embodiments the ram air circuit furthercomprises a divider positioned to separate the ram air shell into afirst region and a second region, wherein two distinct mediums areconfigured to flow through the first region and the second region,respectively.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one heat exchangerincludes a first portion arranged within the first region and a secondportion arranged within the second region, the first portion and thesecond portion being integrally formed.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one heat exchangerincludes a first heat exchanger arranged within the first region and asecond, distinct heat exchanger arranged within the second region, thesecond heat exchanger being arranged in fluid communication with anoutlet of the first heat exchanger.

According to an embodiment, a compressing device for use in anenvironmental control system includes at least one turbine configured toprovide energy by expanding one or more mediums. The one or more mediumsprovided at an outlet of the at least one turbine form a heat sinkwithin the environmental control system. A compressor is configured toreceive energy from the one or more mediums expanded across the at leastone turbine. During a first mode of the compressing device, energyderived from a first medium and a second medium of the one or moremediums is used to compress a second medium at the compressor. During asecond mode of the compressing device, energy derived from the firstmedium, the second medium, and a third medium of the one or more mediumsis used to compress the second medium at the compressor.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one turbine includes afirst turbine configured to receive and extract work from the firstmedium and a second turbine configured to receive and extract work fromthe third medium.

In addition to one or more of the features described above, or as analternative, in further embodiments the first medium is mixed with thethird medium at a location downstream from an outlet of both the firstturbine and the second turbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the first turbine and the secondturbine are arranged in series such that the second turbine is alsoconfigured to receive and extract work from the first medium.

In addition to one or more of the features described above, or as analternative, in further embodiments the first medium output from thefirst turbine is mixed with the third medium at a location upstream fromthe second turbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the second turbine includes a firstnozzle for receiving the first medium and a second nozzle for receivingthe third medium.

In addition to one or more of the features described above, or as analternative, in further embodiments the first medium is mixed with thethird medium at an outlet of the second turbine.

In addition to one or more of the features described above, or as analternative, in further embodiments the at least one turbine furthercomprises a third turbine configured to receive and extract work fromthe second medium.

In addition to one or more of the features described above, or as analternative, in further embodiments the second turbine and the thirdturbine are mounted at opposite ends of the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 is a simplified schematic of a system according to an embodiment;

FIG. 2 is a simplified schematic of a system according to anotherembodiment;

FIG. 3 is a simplified schematic of a system according to anotherembodiment;

FIG. 4 is a simplified schematic of a system according to anotherembodiment;

FIG. 5 is a simplified schematic of a system according to anotherembodiment; and

FIG. 6 is a simplified schematic of a system according to anotherembodiment.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

Embodiments herein provide an environmental control system of anaircraft that mixes mediums from different sources to power theenvironmental control system and to provide cabin pressurization andcooling at a high fuel burn efficiency. The medium can generally be air,while other examples include gases, liquids, fluidized solids, orslurries.

With reference now to the figures, various schematic diagrams of aportion of an environment control system (ECS) 20, such as an airconditioning unit or pack for example, is depicted according tonon-limiting embodiments. Although the environmental control system 20is described with reference to an aircraft, alternative applications arealso within the scope of the disclosure. As shown in the figures, thesystem 20 can receive a first medium A1 at a first inlet 22. Inembodiments where the environmental control system 20 is used in anaircraft application, the first medium A1 is bleed air, which ispressurized air originating from i.e. being “bled” from, an engine orauxiliary power unit of the aircraft. It shall be understood that one ormore of the temperature, humidity, and pressure of the bleed air canvary based upon the compressor stage and revolutions per minute of theengine or auxiliary power unit from which the air is drawn.

The system 20 is also configured to receive a second medium A2 at aninlet 24 and may provide a conditioned form of at least one of the firstmedium A1 and the second medium A2 to a volume 26. In an embodiment, thesecond medium A2 is fresh air, such as outside air for example. Theoutside air can be procured via one or more scooping mechanisms, such asan impact scoop or a flush scoop for example. Thus, the inlet 24 can beconsidered a fresh or outside air inlet. In an embodiment, the secondmedium is ram air drawn from a portion of a ram air circuit to bedescribed in more detail below. Generally, the second medium A2described herein is at an ambient pressure equal to an air pressureoutside of the aircraft when the aircraft is on the ground and isbetween an ambient pressure and a cabin pressure when the aircraft is inflight.

The system 20 can further receive a third medium A3 at an inlet 28. Inone embodiment, the inlet 28 is operably coupled to a volume 26, such asthe cabin of an aircraft, and the third medium A3 is cabin dischargeair, which is air leaving the volume 26 and that would typically bedischarged overboard. In some embodiments, the system 20 is configuredto extract work from the third medium A3. In this manner, thepressurized air A3 of the volume 26 can be utilized by the system 20 toachieve certain operations.

The environmental control system 20 includes a RAM air circuit 30including a shell or duct, illustrated schematically in broken lines at32, within which one or more heat exchangers are located. The shell 32can receive and direct a medium, such as ram air for example, through aportion of the system 20. The one or more heat exchangers are devicesbuilt for efficient heat transfer from one medium to another. Examplesof the type of heat exchangers that may be used, include, but are notlimited to, double pipe, shell and tube, plate, plate and shell,adiabatic shell, plate fin, pillow plate, and fluid heat exchangers.

The one or more heat exchangers arranged within the shell 32 may bereferred to as ram heat exchangers. In the illustrated, non-limitingembodiment, the ram heat exchangers include a first or primary heatexchanger 34 and a second or secondary heat exchanger 36. Within theheat exchangers 34, 36, ram air, such as outside air for example, actsas a heat sink to cool a medium passing there through, for example thefirst medium A1 and/or the second medium A2.

A fan 38 is a mechanical device that can force via push or pull methodsa medium, such as ram air for example, through the shell 32 across theone or more ram heat exchangers 34, 36 at a variable cooling flow rateto control temperatures. As shown, the fan 38 is a separate componentdriven by any suitable means. Examples of such a fan include anelectrically driven fan, a tip turbine fan, or a fan that is part of asimple cycle machine. However, in other embodiments, the fan 38 may partof a compression device 40 to be described in more detail below.

The system 20 additionally includes a compression device 40. In theillustrated, non-limiting embodiment, the compression device 40 is amechanical device that includes components for performing thermodynamicwork on a medium (e.g., extracts work from or applies work to the firstmedium A1, the second medium A2, and/or the third medium A3 by raisingand/or lowering pressure and by raising and/or lowering temperature).Examples of a compression device 40 include an air cycle machine, atwo-wheel air cycle machine, a three-wheel air cycle machine, afour-wheel air cycle machine, etc.

In the non-limiting embodiment of FIGS. 1-4, the compression device 40is a four-wheel air cycle machine including a compressor 42 and aplurality of turbines. The compressor 42 is a mechanical deviceconfigured to raise a pressure of a medium and can be driven by anothermechanical device (e.g., a motor or a medium via a turbine). Examples ofcompressor types include centrifugal, diagonal or mixed-flow,axial-flow, reciprocating, ionic liquid piston, rotary screw, rotaryvane, scroll, diaphragm, air bubble, etc. As shown, the compressor 42 isconfigured to receive and pressurize the second medium A2.

In the illustrated embodiment, the compression device 40 includes aturbine 44, such as a fresh air turbine, a bleed turbine 46, and a powerturbine 48 operably coupled to each other and the compressor 42 via ashaft 50. The turbines 44, 46, and 48 are mechanical devices that expanda medium and extract work therefrom (also referred to as extractingenergy) to drive the compressor 42 via the shaft 50. The turbines 44,46, and 48 are operable independently or in combination, to drive thecompressor 42 via the shaft 50.

The system 20 additionally includes a dehumidification system. In theillustrated, non-limiting embodiment of FIG. 1, the dehumidificationsystem includes a condenser 52 and a water extractor or collector 54arranged downstream from the condenser 52. The condenser 52 and thewater collector 54 may be arranged in fluid communication with thesecond medium A2. The condenser 52 is a particular type of heatexchanger and the water collector 54 is a mechanical device thatperforms a process of removing water from a medium. In the non-limitingembodiment of FIGS. 1, 3, and 5, the condenser 52 of thedehumidification system is illustrated as a separate heat exchangerlocated downstream from and arranged in fluid communication with anoutlet of the second heat exchanger 36. However, the configuration ofthe at least one dehumidification system may vary.

In the non-limiting embodiments of FIGS. 2, 4, and 6, the condenser 52is formed integrally with the secondary heat exchanger 36. For example,the second medium A2 is configured to flow through a first portion ofthe heat exchanger that forms the secondary heat exchanger, and thenthrough a second, downstream portion of the heat exchanger, which formsthe condenser. In such embodiments, although the entire heat exchangeris arranged within the ram air shell 32, a divider 56 wall may extendparallel to the flow of ram air through the shell 32 at the interfacebetween the first and second portions of the heat exchanger to separatethe ram air shell 32 into a distinct first region 58 and second region59. Accordingly, the fan 38 is positioned to draw ram air through onlythe first region 58, across the primary heat exchanger 34 and the firstportion that forms a secondary heat exchanger 36. A fluid flow, distinctfrom the ram air flow to be described in more detail below, isconfigured to flow through the second region 59, across the secondportion of the heat exchanger that forms the condenser 52. In such aconfiguration, the ram air arranged within the first region 58 and thefluid flow provided to the second region 59 do not mix within the ramair shell 32. However, it should be understood that embodiments wherethe secondary heat exchanger 36 is arranged within the first region 58,and a condenser 52, separate from and arranged in fluid communicationwith an outlet of the secondary heat exchanger 36, is arranged withinthe second region 59 are also within the scope of the disclosure.

The elements of the system 20 are connected via valves, tubes, pipes,and the like. Valves (e.g., flow regulation device or mass flow valve)are devices that regulate, direct, and/or control a flow of a medium byopening, closing, or partially obstructing various passageways withinthe tubes, pipes, etc. of the system. Valves can be operated byactuators, such that flow rates of the medium in any portion of thesystem 20 can be regulated to a desired value. For instance, a firstvalve V1 may be configured to control a supply of the first medium A1 tothe system 20, and a second valve may be operable to allow a portion ofa medium, such as the first medium A1, to bypass the ram air circuit 30.As a result, operation of the second valve V2 may be used to add heat tothe system 20 and to drive the compression device 40 when needed. Athird valve V3 may be operable in the event of a pack failure, such aswhere the system 20 does not have a sufficient flow of the second mediumA2 to meet the demands of the cabin or other loads. In such instances,operation of valve V3 may be used to supplement the flow of secondmedium A2 with first medium A1, such as at a location upstream from thedehumidification system for example, to meet the demands of theaircraft.

Operation of a fourth valve V4 may be used to allow a portion of thesecond medium A2 to bypass the dehumidification system and the turbine44 of the compression device 40 and operation of a fifth valve V5 may beconfigured to allow a portion of the second medium A2 output from thedehumidification system to bypass the turbine 44 of the compressiondevice 40. In an embodiment, a sixth valve V6 is a surge control valve,operable to exhaust a portion of the second medium A2 output from thecompressor 42 overboard or into the ram air circuit 30 to prevent acompressor surge. In an embodiment, a seventh valve V7 is configured tocontrol a supply of a medium, such as the first medium A1 for example,to the fan 38, to drive operation of the fan 38. A valve V8 may beconfigured to control a supply of the third medium A3 to the system 20,

With continued reference to FIGS. 1 and 2, the system 20 is operable ina plurality of modes, selectable based on a flight condition of theaircraft. For example, the system 20 may be operable in a first, lowaltitude mode or a second, high altitude mode. The first, low altitudemode is typically used for ground and low altitude flight conditions,such as ground idle, taxi, take-off, and hold conditions, and thesecond, high altitude mode may be used at high altitude cruise, climb,and descent flight conditions.

In the first, low altitude mode, valve V1 and V7 are open, and a highpressure first medium A1, such as bleed air drawn from an engine or APU,is provided to the primary heat exchanger 34 and to the fan 38. Withinthe first heat exchanger 34, the first medium A1 is cooled via a flow ofram air, driven by the fan 38. As shown in FIG. 1, the cool first mediumpasses sequentially from the first heat exchanger 34 to another heatexchanger 60, where the first medium A1 is further cooled by anothermedium, distinct from the ram air. In other embodiments, best shown inFIG. 2, the heat exchanger 60 may be integrally formed with the heatexchanger that functions as the primary heat exchanger 34 and ispositioned within the second region 59 of the ram air circuit 30.

From the heat exchanger 60, the further cooled first medium A1 isprovided to the inlet of the bleed turbine 46. The high pressure firstmedium A1 is expanded across the bleed turbine 46 and work is extractedtherefrom. The first medium A1 output from the bleed turbine 46 has areduced temperature and pressure relative to the first medium A1provided to the inlet of the bleed turbine 46. The first medium A1 atthe outlet of the bleed turbine 46 may be used to cool the second mediumA2 within the condenser 52, to be described in more detail below, and/orto cool the first medium A1 within the heat exchanger 60. This coolingmay occur separately from (FIG. 1) or within the second region 59 of theram air circuit 30 (FIG. 2). After receiving heat from the first mediumA1 within heat exchanger 60, the first medium A1 may be exhaustedoverboard or outside the aircraft, or to a portion of the ram aircircuit 30, such as downstream from all of the heat exchangers arrangedtherein. In an embodiment, best shown in FIG. 2, a wall or barrier 61may be arranged at an upstream end of the second region 59 to preventanother medium, separate from the medium output from the compressingdevice 40 from passing through the second region 59. Although such abarrier 61 is illustrated in FIG. 2, it should be understood that any ofthe embodiments of the ram air system including a separate first andsecond region 58, 59 may include such a barrier 61.

The work extracted form the first medium A1 in the bleed turbine 46,drives the compressor 42, which is used to compress a second medium A2provided from an aircraft inlet 24. As shown, the second medium A2, suchas fresh air for example, is drawn from an upstream end of the ram aircircuit 30 or from another source and provided to an inlet of thecompressor 42. The act of compressing the second medium A2, heats thesecond medium A2 and increases the pressure of the second medium A2.

In some embodiments, the compressed second medium A2 output from thecompressor 42 is provided to an ozone removal heat exchanger 62, beforebeing provided to the secondary heat exchanger 36 where it is cooled byram air. In the illustrated, non-limiting embodiment, the first mediumA1 and the second medium A2 are configured to flow through the primaryand second heat exchangers 34, 36, respectively, in the same directionrelative to the ram air flow. However, embodiments where the first andsecond medium flow in different directions are also within the scope ofthe disclosure.

The second medium A2 exiting the secondary heat exchanger 36 is thenprovided to the condenser 52, where the second medium A2 is furthercooled by the first medium A1 output from the bleed turbine 46. From thecondenser 52, the second medium A2 is provided to the water collector 54where any free moisture is removed, to produce cool medium pressure air.This cool pressurized second medium A2 then enters the turbine 44 wherework is extracted from the second medium A2 and used to drive thecompressor 42. The second medium output from the turbine 44 is then sentto one or more loads of the aircraft, such as to condition thepressurized volume or cabin 26.

The high-altitude mode of operation is similar to the low altitude modeof operation. However, in some embodiments, valve V2 may be open toallow at least a portion of the first medium A1 to bypass the primaryheat exchanger 34 and heat exchanger 60. Valve V2 may be operated tocontrol, and in some embodiments, maximize the temperature of the firstmedium A1 provided to the bleed turbine 46. As a result, the workextracted from the first medium A1 within the bleed turbine 46 may beoptimized while exhausting the first medium A1 therefrom with atemperature suitable to function as a heat sink with respect to thecondenser 52 and/or heat exchanger 60.

In the high-altitude mode of operation, the third medium A3, such as anexhaust of cabin air for example, is recirculated to the system 20 fromthe pressurized volume 26, through valve V8. The flow of the thirdmedium A3 may be provided directly to an inlet of the power turbine 48.The additional work extracted from the third medium A3 in the powerturbine 48, is used in combination with the work extracted from thefirst medium A1 to drive the compressor 42. As shown, the third mediumA3 may be mixed at a mixing point MP1 with the first medium A1. In theillustrated, non-limiting embodiment, the mixing point is locateddownstream from an outlet of the bleed turbine 46 and the power turbine48. In the high altitude mode of operation, this mixture of first mediumand third medium A1+A3 may be used to cool the second medium A2 withinthe condenser 52, and/or to cool the first medium A1 within the heatexchanger 60, and then dumped overboard or into the ram air circuit 30.

The compressed second medium A2 output from the compressor 42 may followthe same flow path with respect to the secondary heat exchanger 36 andcondenser 52, water collector 54, and turbine 44 as previously describedfor the low altitude mode of operation. However, in an embodiment, valveV5 is open in the high-altitude mode. As a result, at least a portion ofthe second medium A2 output from the condenser 52 bypasses the turbine44 of the compression device.

Depending on the temperature and humidity conditions of the day, thesecond medium output from the condenser 52 may be too cold to providedirectly to the cabin 26, via valve V5. In such instances, during thehigh-altitude mode of operation, valve V4 is opened, thereby allowing aportion of the heated second medium A2 output from the compressor 42 tomix with the cold second medium A2 upstream from an outlet of the system20. Accordingly, valve V4 can be controlled to achieve a second mediumA2 having a desired temperature for conditioning the cabin 26.

With reference now to FIGS. 3 and 4, another configuration of the system20 is illustrated. The system 20 is similar to the configuration ofFIGS. 1 and 2; however, in the illustrated, non-limiting embodiment, thecompression device 40 includes a second bleed turbine 46 b in place ofthe power turbine 48. Accordingly, during both the low altitude andhigh-altitude modes of operation, the first medium A1 is provided to thefirst bleed turbine 46 a then to the second bleed turbine 46 bsequentially. The work extracted from the first medium A1 in both bleedturbines 46 a, 46 b is used to drive the compressor. Further, the firstmedium A1 output from the second bleed turbine 46 b is used to cool theflows of medium within the condenser 52 and/or the heat exchanger 60. Aspreviously described, in a high-altitude mode of operation, the thirdmedium A3 is additionally provided to the system 20 and work isextracted therefrom. As shown, the third medium A3 is mixed at a mixingpoint MP2 with the first medium A1. In the illustrated, non-limitingembodiment, the mixing point MP2 is located downstream from an outlet ofthe first bleed turbine 46 a and upstream from an inlet of the secondbleed turbine 46 b. By mixing the plurality of mediums within the aircycle machine, the complexity of the housing of the compressing device40 a is reduced since only a single outlet for both the first medium andthe third medium is formed therein.

In an embodiment, the pressure ratio of one or more of the turbines ofthe compressing device 40 is reduced relative to existing turbines. Asused herein, the term “pressure ratio” is intended to describe the ratioof the pressure of the medium provided to an inlet of the turbine andthe pressure of the medium provided at the outlet of the turbine. In anembodiment, such as embodiments of the system 20 including a pluralityof turbines 46 a, 46 b arranged in series relative to a flow of one ormore mediums, the pressure ratio of each of the turbines may be reducedcompared to conventional turbines.

Yet another configuration of the system 20 is illustrated in thenon-limiting embodiment of FIGS. 5 and 6. As shown, the system 20 issubstantially similar to the previous configurations. However, thecompression device 40 of the system 20 of FIGS. 5 and 6 includes a dualentry turbine 70 in place of the power turbine or the second bleedturbine. As shown, the dual entry turbine 70 is configured to receiveflows of different mediums. A dual entry turbine typically has multiplenozzles, each of which is configured to receive a distinct flow ofmedium at a different entry point, such that multiple flows can bereceived simultaneously. For example, the turbine 70 can include aplurality of inlet flow paths, such as an inner flow path and an outerflow path, to enable mixing of the medium flows at the exit of theturbine 70. The inner flow path can be a first diameter, and the outerflow path can be a second diameter. Further, the inner flow path canalign with one of the first or second nozzles, and the outer flow pathcan align with the other of the first or second nozzles.

In an embodiment, one of the inlets or nozzles of the dual entry turbine70 is arranged downstream from and in series with an outlet of the bleedturbine 46. Accordingly, during both the low altitude and high-altitudemodes of operation, the first medium A1 is provided to bleed turbine 46then to the dual entry turbine 70 sequentially. The work extracted fromthe first medium A1 in both the bleed turbine 46 and the dual entryturbine 70 is used to drive the compressor. Further, the first medium A1output from the second bleed turbine 46 b is used to cool the flows ofmedium within the condenser 52 and/or the heat exchanger 60. Aspreviously described, in a high-altitude mode of operation, the thirdmedium A3 is additionally provided to the system 20 and work isextracted therefrom. As shown, the third medium A3 may be provided to asecond inlet or nozzle of the dual entry turbine 70. In suchembodiments, the mixing point MP3 of the third medium A3 and the firstmedium A1 can be at the dual entry turbine 70, such as at an outlet ofthe turbine 70 for example, or alternatively, may be downstreamtherefrom.

The term “about” is intended to include the degree of error associatedwith measurement of the particular quantity based upon the equipmentavailable at the time of filing the application.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof.

While the present disclosure has been described with reference to anexemplary embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

What is claimed is:
 1. A compressing device for use in an environmentalcontrol system comprising: at least one turbine configured to provideenergy by expanding one or more mediums, wherein the one or more mediumsprovided at an outlet of the at least one turbine form a heat sinkwithin the environmental control system; a compressor configured toreceive energy from the one or more mediums expanded across the at leastone turbine, wherein during a first mode of the compressing device,energy derived from a first medium and a second medium of the one ormore mediums is used to compress a second medium at the compressor andduring a second mode of the compressing device, energy derived from thefirst medium, the second medium, and a third medium of the one or moremediums is used to compress the second medium at the compressor.
 2. Thecompressing device of claim 1, wherein the at least one turbine includesa first turbine configured to receive and extract work from the firstmedium and a second turbine configured to receive and extract work fromthe third medium.
 3. The compressing device of claim 2, wherein thefirst medium is mixed with the third medium at a location downstreamfrom an outlet of both the first turbine and the second turbine.
 4. Thecompressing device of claim 2, wherein the first turbine and the secondturbine are arranged in series such that the second turbine is alsoconfigured to receive and extract work from the first medium.
 5. Thecompressing device of claim 4, wherein the first medium output from thefirst turbine is mixed with the third medium at a location upstream fromthe second turbine.
 6. The compressing device of claim 4, wherein thesecond turbine includes a first nozzle for receiving the first mediumand a second nozzle for receiving the third medium.
 7. The compressingdevice of claim 6, wherein the first medium is mixed with the thirdmedium at an outlet of the second turbine.
 8. The compressing device ofclaim 2, wherein the at least one turbine further comprises a thirdturbine configured to receive and extract work from the second medium.9. The compressing device of claim 8, wherein the second turbine and thethird turbine are mounted at opposite ends of the shaft.